The present invention relates generally to a temperature sensor and, more specifically, to a fiber optic temperature sensor capable of measuring a wide range of temperatures.
In various applications such as supersonic or hypersonic aircraft, it is desirable to measure temperatures over a large temperatures range using a single sensor. The desired temperature range for such applications may reach as low as -50.degree. C. and extend up to about 1,000.degree. C.
Conventional temperature measuring devices such as thermistors, thermocouples and bi-metal type devices are undesirable for use in aircraft applications. Such devices are vulnerable to electromagnetic interference, are heavy and may cause sparking.
Sensors employing optical fibers have been used for various applications. Fiber optic sensors are lighter in weight than conventional sensors, are not susceptible to electromagnetic interference, possess larger band widths and have increased safety due to being less susceptible to sparking. Known fiber optic sensors include pyrometric sensors which measure the radiant energy from a body. Pyrometric sensors are particularly suited for relatively high temperatures. Florescent decay sensors are another type of fiber optic sensors. One problem with these conventional fiber optic sensors is that they possess inadequate dynamic range, lack measurement stability and have an unacceptably short lifetime.
One problem common to all temperature sensing devices is that complex calibration procedures are required when the devices are replaced. Such calibration procedures require a significant amount of time to implement in the aircraft industry. In particular, an easy or no calibration procedure is highly desirable so that a sensor may easily be removed and replaced while requiring a minimum amount of aircraft down time.
It is therefore desirable to provide a temperature sensor which has a large temperature range is immune from electromagnetic interference, is lightweight, accurate and long-lived.